A general solid-oxide type fuel cell uses an oxide ion conductive material as electrolyte and requires an operating temperature of 500° C. or more to obtain ion conductivity. Accordingly, the solid-oxide type fuel cell, which requires warm-up time in the case of cold-start, has been conventionally used mainly for stationary equipment with a low frequency of cold-start.
Accordingly, in view of adapting the aforementioned fuel cell to a mobile body, there has been proposed a multi-stage fuel cell system having small fuel cells and large fuel cells in order to support both quick startability and high output required for a mobile body (see Patent Literature 1).